The military applications of self-replicating micro- and nanotechnology were realised very early in the Interplanetary Age, especially against soft targets (organic materials and unprotected infrastructure particularly). Such military nanoswarm weapons became popularly known as Khaki Goo. Early on, and into the present day, various treaties against their development or deployment have been in force, though they inevitably do have their failures and limitations. Equally early, in recognition of the fact that agreements can fail, and also in recognition of the fact that the most devastating forms of Khaki Goo might themselves even turn on those who have deployed them, defence systems against aggressive nanoswarms were quickly developed.
Early khaki goo was limited in its usefulness by the amount of stored energy each bot could carry, and in many other ways, though many of those limitations have been overcome. In space warfare for instance an Interplanetary Age nanoswarm weapon did not have enough stored energy to quickly assemble or disassemble iron-hulled craft. All hull ports and openings could be easily protected by periodic EMP sterilisation, although this would decrease the utility of any data flow through such a port. Habitats were more vulnerable, however, as so much material must flow in and out of an inhabited structure. This meant careful scans of ingoing cargo as well as careful vetting of any incoming software intended for any of the hab’s nanofacs. Once established, physical or software infestations can be difficult to remove, particularly if they are programmed to lie dormant and if they attack vulnerable targets such as personnel, consumables, and data resources. On a planetary surface (or later in history, on megahabs) khaki goo is even more difficult to control; bionanotech Khaki Goo may hide in the local ecosystem, and drytech Khaki Goo may be disguised within the mechosystem. Early and primitive Blue Goo had very limited effectiveness in large environments, and it was only with the advent of Blue Goo developed by GAIA that the terms became more equal.
In the millennia since the arms race has continued between Khaki and Blue goo. Sporetech in general and in particular advanced forms of energy storage allow tiny devices to retain very large amounts of energy, enough to attack (or defend) almost any target. The local balance can tip this way or that as novel new techniques are developed. A recent instance of a nanoswarm disaster is the one that occurred at Swallowflight, leading to the establishment of the Vela Immunity.
Nanoswarm weapons remain a constant danger, just as genetically engineered diseases remain a risk, and data viral infections likewise; all such forms of infection must be resisted by immune defences that are constantly upgraded.